As population and urban development expand in land scarce island countries (or countries with long coastlines), city planners and engineers may resort to land reclamation to ease the pressure on existing heavily-used land and underground spaces. Using fill materials from seabed, hills, deep underground excavations, and even construction debris, engineers are able to create relatively vast and valuable land from the sea. However, land reclamation has its limitations. It is only suitable when the water depth is shallow (less than 20 m). When the water depth is large and/or the seabed is extremely soft, land reclamation may no longer be cost effective or even feasible. Moreover, land reclamation may destroy the marine habitat and may even lead to the disturbance of toxic sediments.
Very Large Floating Structures (VLFS) are an alternative method to create “land” on the sea. There are two types of VLFS; the semisubmersible-type and the pontoon-type. Semi-submersible type floating structures are raised above the sea level using column tubes or ballast structural elements to minimize the effects of waves while maintaining a constant buoyancy force. Thus they can reduce the wave induced motions and are therefore suitably deployed in high seas with large waves. Floating-platforms used for drilling for and production of oil and gas are typical examples of semi-submersible-type VLFSs. When these semi-submersibles are attached to the seabed using vertical tethers with high pretension as provided by additional buoyancy of the structure, they are referred to as tension-leg platforms.
In contrast, pontoon-type floating structures lie on the sea level and are typically for use in calm waters, often inside a cove or a lagoon and near the shoreline. The larger category of pontoon-type floating structures or Mega-Floats have at least one length dimensions greater than 60 m.
When a Mega-Float is heavily loaded, in the central portion for example, the floating structure will deflect with the centre vertically displaced relative to the corners. The resulting differential deflection may cause equipment to malfunction, the superstructure on the floating structure to be subjected to additional stresses or in extreme cases may lead to structural failure under high stress conditions.
A need therefore exists to address at least one of the above problems.